Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2001-08-03
2002-12-31
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S632000, C359S633000, C359S637000
Reexamination Certificate
active
06501602
ABSTRACT:
This application claims benefit of Japanese Application No. 2000-239630 filed in Japan on Aug. 8, 2000, the contents of which are incorporated by this reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image display apparatus having a three-dimensionally decentered optical path. More particularly, the present invention relates to a head- or face-mounted image display apparatus that can be retained on an observer's head or face and allows observation of the image of a single image display device with two eyes.
2. Discussion of Related Art
Image display apparatus designed to observe the image of a single image display device with two eyes have heretofore been known in Japanese Patent Application Unexamined Publication Nos. [hereinafter referred to as “JP(A)”] 6-110013, 7-287185, 9-61748, 9-181998, and 9-181999, Published Japanese Translation of PCT International Publication No. Hei 10-504115, etc.
Among them, the image display apparatus of JP(A) 6-110013 splits and folds light rays by using a prism in the shape of an isosceles triangular prism and a mirror. Therefore, correction of various aberrations is performed by using a lens placed in front of the pupil. This makes it difficult to correct aberrations, and at the same time, causes the apparatus to become large in size. JP(A) 7-287185 uses a plurality of mirrors and performs image formation with a single convex lens. Therefore, it is very difficult to perform assembly adjustment. In addition, appropriate performance cannot be attained. Although the image display device is placed three dimensionally, the optical systems for the left and right eyes are in bilateral symmetry with each other. Therefore, the images of the image display device that are displayed in the left and right eyes are in oppositely rotated relation to each other.
In JP(A) 9-61748, display light from an LCD (Liquid Crystal Display) is split by using a half-mirror so as to be observed with two eyes. Because the display light is distributed to the left and right eyeballs, the image for observation is weak in light intensity and hence dark. In JP(A) 9-181998 and 9-181999, optical paths for two eyes are provided sidewardly of the image display device. Therefore, the tilt angle of the principal rays with respect to the image display device is very large. Accordingly, these apparatus cannot use an ordinary LCD (Liquid Crystal Display) because the viewing angle thereof is not sufficiently wide.
The image display apparatus of Published Japanese Translation of PCT International Publication No. Hei 10-504115 splits display light by using a half-mirror. The image display apparatus has a very large number of components and requires a very complicated assembling operation.
Recently, with the achievement of small-sized image display devices, it has become necessary to reduce the focal length of the viewing optical system in order to ensure the same field angle. However, if the focal length is shortened, it becomes difficult to ensure the required back focus, and it becomes impossible to increase the optical path length within the prism. As a result, it becomes impossible to increase the number of reflecting surfaces and hence impossible to correct decentration aberrations satisfactorily.
Further, with the recent development of manufacturing techniques, image display devices are becoming higher in definition year by year.
SUMMARY OF THE INVENTION
The present invention was made in view of the above-described problems with the prior art.
Accordingly, an object of the present invention is to provide an image display apparatus, e.g. a head-mounted image display apparatus, in which an image from a single image display device is led to two eyes without using a half-mirror, thereby allowing observation of a bright image, and in which at least three curved reflecting surfaces are used to form an optical system, thereby allowing correction of various aberrations in conformity to recent compact and high-definition image display devices.
Another object of the present invention is to provide an image display apparatus favorably improved in terms of the tilt angle of the principal rays with respect to the image display device.
To attain the above-described objects, the present invention provides an image display apparatus having a three-dimensionally decentered optical path. The image display apparatus includes an image display device for forming an image for observation on an image display area. The image display apparatus further includes a viewing optical system for leading the image formed by the image display device to a pupil corresponding to a position where an eyeball of an observer is to be placed.
The image display device is a single image display device having a plurality of pixels juxtaposed on a single substrate.
Each pixel located at least in the central portion of the single image display device is arranged to emit an image light beam at such an exit angle that the light beam can be led to the left and right eyes of the observer.
The viewing optical system includes at least a left ocular part for leading the light beam to the left eye of the observer; a right ocular part for leading the light beam to the right eye of the observer; and an optical path distributing part for distributing the image light beam emitted from the image display device at the above-described exit angle to the left and right ocular parts.
The left ocular part has at least two reflecting surfaces. At least one of the at least two reflecting surfaces is formed from a rotationally asymmetric curved reflecting surface having the function of correcting decentration aberrations.
The right ocular part has at least two reflecting surfaces. At least one of the at least two reflecting surfaces is formed from a rotationally asymmetric curved reflecting surface having the function of correcting decentration aberrations.
The optical path distributing part has at least one pair of reflecting surfaces for left and right optical paths for the left and right eyes of the observer. The reflecting surfaces are each formed from a rotationally asymmetric curved reflecting surface having the function of correcting decentration aberrations.
The left and right optical paths of the viewing optical system are formed by optical surfaces arranged so that the left and right optical paths are not in plane symmetry with each other but in 180-degree rotational symmetry with respect to only a normal line passing through the center of the image display device.
The reasons for adopting the above-described arrangement in the present invention, together with the function thereof, will be described below.
FIG. 1
shows the left and right optical paths (for the left and right eyes) and optical surfaces of the viewing optical system in the image display apparatus according to Example 1 (described later). Part (a) of
FIG. 1
is a plan view. Part (b) of
FIG. 1
is a side view. In the figure, L and R are suffixed to reference symbols to distinguish between the left and right optical surfaces, axial principal rays and pupils. The reference symbols are put to the constituent elements in the order of backward ray tracing to match with the description of numerical data (shown later).
The viewing optical system includes a left ocular part
10
L for leading a light beam to an observer's left eye positioned at a left pupil
1
L and a right ocular part
10
R for leading a light beam to an observer's right eye positioned at a right pupil
1
R. The viewing optical system further includes an optical path distributing part (optical path distributing prism in Example 1, which is shown in
FIG. 1
)
20
for leading an image light beam emitted from an image display device
3
at a predetermined exit angle to the left and right ocular parts
10
L and
10
R.
The left and right ocular parts
10
L and
10
R each have at least two reflecting surfaces (back-coated mirrors
12
L and
12
R and totally reflecting surfaces
13
L and
13
R in the case of FIG.
1
). At least one of the at least
Nagata Tetsuo
Togino Takayoshi
Mack Ricky
Olympus Optical Co,. Ltd.
Pillsbury & Winthrop LLP
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